Go Premium for a chance to win a PS4. Enter to Win

x
  • Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 406
  • Last Modified:

Casting in Java, why?

Hello Experts,

This is what I expect to be a 'noob' question, but I cannot figure out why I need to Cast this object.  I have a button in my Android app and apparently have to Cast the object...why?  Code below:
Button b = (Button) findViewById(R.id.button1);

Open in new window

FYI...I'm following a tutorial on Lynda.com and this was mentioned as important.  I would really appreciate any help to understand 'why' it needs to be Cast as a button when it IS a button already and b was type cast as a button too.

Thank you.
0
Modifier1000
Asked:
Modifier1000
1 Solution
 
ksivananthCommented:
though the actual view is a button, the return type of findViewById is different than Button.
0
 
BenefordCommented:
findViewById() is actually returning a View object (a Button is a subclass of TextView which is a subclass of View)
You know that the View returned is a Button, but the Java sysem can't work that out just by looking at the source code. The type check system tries to stop you doing things that aren't going to work (very useful most of the time), and the cast is how you tell the type check system that you really do know what's going on.
0
 
Modifier1000Author Commented:
Thank you for the explanation, very helpful in giving more depth to your answer.
0

Featured Post

Free Tool: Site Down Detector

Helpful to verify reports of your own downtime, or to double check a downed website you are trying to access.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Tackle projects and never again get stuck behind a technical roadblock.
Join Now